Publisher: SciELO   (Total: 887 journals)

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Showing 201 - 400 of 887 Journals sorted alphabetically
Cubo. A Mathematical J.     Open Access  
Cuestiones Constitucionales     Open Access   (Followers: 2, SJR: 0.1, CiteScore: 0)
Cuicuilco     Open Access   (Followers: 1)
Cuicuilco. Revista de Ciencias Antropológicas     Open Access  
Cultivos Tropicales     Open Access   (Followers: 1)
Cultura y Representaciones Sociales     Open Access  
Culturales     Open Access   (Followers: 3)
Dados - Revista de Ciências Sociais     Open Access   (SJR: 0.37, CiteScore: 0)
De Jure     Open Access   (Followers: 1)
DELTA : Documentação de Estudos em Lingüística Teórica e Aplicada     Open Access   (SJR: 0.133, CiteScore: 0)
Dementia & Neuropsychologia     Open Access   (Followers: 10, SJR: 0.205, CiteScore: 0)
Dental Press J. of Orthodontics     Open Access   (Followers: 5, SJR: 0.489, CiteScore: 1)
Desacatos     Open Access   (Followers: 1)
Desacatos : Revista de Antropología Social     Open Access  
Desarrollo y Sociedad     Open Access   (Followers: 3, SJR: 0.109, CiteScore: 0)
Diálogo Andino - Revista de Historia, Geografía y Cultura Andina     Open Access   (Followers: 1, SJR: 0.116, CiteScore: 0)
Diánoia     Open Access   (Followers: 1)
Dimensión Empresarial     Open Access  
Discusiones Filosóficas     Open Access  
Dynamis : Acta Hispanica ad Medicinae Scientiarumque Historiam Illustrandam     Open Access   (Followers: 3, SJR: 0.131, CiteScore: 0)
e-J. of Portuguese History     Open Access   (Followers: 2, SJR: 0.101, CiteScore: 0)
e-Pública : Revista Eletrónica de Direito Público     Open Access  
Earth Sciences Research J.     Open Access  
Eclética Química     Open Access   (Followers: 1)
Ecología en Bolivia     Open Access  
Economia Aplicada     Open Access   (SJR: 0.208, CiteScore: 0)
Economia e Sociedade     Open Access  
EconoQuantum     Open Access  
Educação & Sociedade     Open Access   (Followers: 3)
Educação e Pesquisa     Open Access   (Followers: 1, SJR: 0.163, CiteScore: 0)
Educação em Revista     Open Access  
Educación Matemática     Open Access  
Educación Médica     Open Access   (Followers: 1, SJR: 0.236, CiteScore: 0)
Educación Médica Superior     Open Access   (Followers: 1, SJR: 0.237, CiteScore: 0)
Educación y Educadores     Open Access  
Educar em Revista     Open Access  
EDUMECENTRO     Open Access  
Eidos     Open Access   (SJR: 0.119, CiteScore: 0)
En-Claves del pensamiento     Open Access   (Followers: 1, SJR: 0.194, CiteScore: 0)
Encuentros     Open Access  
Ene : Revista de Enfermería     Open Access  
Enfermería Global     Open Access   (Followers: 3, SJR: 0.165, CiteScore: 0)
Enfermería Nefrológica     Open Access   (Followers: 1, SJR: 0.198, CiteScore: 0)
Enfoques     Open Access  
Engenharia Agrícola     Open Access   (SJR: 0.305, CiteScore: 1)
Engenharia Sanitaria e Ambiental     Open Access   (SJR: 0.218, CiteScore: 0)
Ensaio Avaliação e Políticas Públicas em Educação     Open Access   (Followers: 1, SJR: 0.254, CiteScore: 0)
Ensayos de Economía     Open Access  
Ensayos Revista de Economía     Open Access  
Entomologia y Vectores     Open Access   (Followers: 2)
Entre Ciencia e Ingeniería     Open Access  
Epidemiologia e Serviços de Saúde     Open Access  
Escritos de Psicología : Psychological Writings     Open Access   (Followers: 2)
Estudios Atacameños     Open Access   (Followers: 2, SJR: 0.446, CiteScore: 1)
Estudios Constitucionales     Open Access   (Followers: 5, SJR: 0.319, CiteScore: 0)
Estudios de Cultura Maya     Open Access   (Followers: 2, SJR: 0.272, CiteScore: 0)
Estudios de Economía     Open Access   (SJR: 0.121, CiteScore: 0)
Estudios de historia moderna y contemporánea de México     Open Access   (SJR: 0.101, CiteScore: 0)
Estudios Economicos     Open Access  
Estudios Filologicos     Open Access   (SJR: 0.107, CiteScore: 0)
Estudios Fronterizos     Open Access   (Followers: 1)
Estudios internacionales     Open Access   (Followers: 5)
Estudios Pedagogicos (Valdivia)     Open Access   (Followers: 1, SJR: 0.338, CiteScore: 0)
Estudios Políticos     Open Access  
Estudios Sociales     Open Access   (Followers: 2)
Estudios sociales : Revista de alimentación contemporánea y desarrollo regional     Open Access  
Estudios Socioterritoriales : Revista de Geografía     Open Access  
Estudos Afro-Asiáticos     Open Access   (Followers: 2)
Estudos Avançados     Open Access   (SJR: 0.232, CiteScore: 0)
Estudos de Psicologia (Campinas)     Open Access   (Followers: 1, SJR: 0.233, CiteScore: 0)
Estudos de Psicologia (Natal)     Open Access   (SJR: 0.117, CiteScore: 0)
Estudos Econômicos     Open Access   (SJR: 0.204, CiteScore: 0)
Estudos Históricos     Open Access   (Followers: 1)
EURE (Santiago) - Revista Latinoamericana de Estudios Urbano Regionales     Open Access   (SJR: 0.38, CiteScore: 1)
Ex aequo     Open Access  
FEM : Revista de la Fundación Educación Médica     Open Access  
Fides et Ratio : Revista de Difusión Cultural y Científica     Open Access  
Fisioterapia e Pesquisa     Open Access  
Fisioterapia em Movimento     Open Access  
Fitosanidad     Open Access  
Floresta e Ambiente     Open Access   (Followers: 1, SJR: 0.3, CiteScore: 0)
Folios     Open Access  
Food Science and Technology (Campinas)     Open Access   (Followers: 1, SJR: 0.467, CiteScore: 1)
Formación Universitaria     Open Access   (Followers: 4, SJR: 0.213, CiteScore: 1)
Frónesis     Open Access  
Frontera Norte     Open Access  
Gaceta Médica Boliviana     Open Access  
Gaceta Médica Espirituana     Open Access  
Galáxia (São Paulo)     Open Access  
Gayana (Concepcion)     Open Access   (SJR: 0.236, CiteScore: 0)
Gayana. Botanica     Open Access   (SJR: 0.234, CiteScore: 0)
Genetics and Molecular Biology     Open Access   (Followers: 15, SJR: 0.638, CiteScore: 2)
Geofísica internacional     Open Access   (SJR: 0.312, CiteScore: 1)
Gerokomos     Open Access   (Followers: 1, SJR: 0.257, CiteScore: 0)
Gestão & Produção     Open Access   (SJR: 0.156, CiteScore: 0)
Gestión y Política Pública     Open Access   (Followers: 2, SJR: 0.106, CiteScore: 0)
Hacia la Promoción de la Salud     Open Access  
Hallazgos     Open Access   (Followers: 1)
Hidrobiológica     Open Access   (SJR: 0.166, CiteScore: 0)
Historia     Open Access   (Followers: 2)
Historia (Santiago)     Open Access   (Followers: 1, SJR: 0.162, CiteScore: 0)
História (São Paulo)     Open Access   (SJR: 0.11, CiteScore: 0)
História, Ciências, Saúde - Manguinhos     Open Access   (Followers: 2, SJR: 0.144, CiteScore: 0)
Hoehnea     Open Access  
Horizonte Sanitario     Open Access  
Horizontes Antropológicos     Open Access   (Followers: 3, SJR: 0.233, CiteScore: 0)
Horticultura Brasileira     Open Access   (SJR: 0.605, CiteScore: 1)
HTS Theological Studies     Open Access   (Followers: 8, SJR: 0.448, CiteScore: 0)
Humanidades Médicas     Open Access  
IDESIA : Revista de Agricultura en Zonas Áridas     Open Access   (SJR: 0.223, CiteScore: 0)
Iheringia. Série Zoologia     Open Access   (Followers: 1, SJR: 0.26, CiteScore: 1)
Íkala : Revista de Lenguaje y Cultura     Open Access   (SJR: 0.112, CiteScore: 0)
Image & Text     Open Access  
Index de Enfermeria     Open Access   (Followers: 5, SJR: 0.113, CiteScore: 0)
Indo-Pacific J. of Phenomenology     Open Access   (Followers: 1)
Infectio     Open Access   (SJR: 0.133, CiteScore: 0)
Información Tecnológica     Open Access   (SJR: 0.197, CiteScore: 0)
Ingeniare : Revista Chilena de Ingenieria     Open Access   (Followers: 1, SJR: 0.239, CiteScore: 0)
Ingeniería Electrónica, Automática y Comunicaciones     Open Access  
Ingeniería Hidráulica y Ambiental     Open Access  
Ingeniería Industrial     Open Access  
Ingeniería Mecánica     Open Access   (Followers: 4)
Ingenieria Mecánica. Tecnologia y Desarrollo     Open Access   (Followers: 3)
Ingeniería y Competitividad     Open Access  
Ingenieria y Universidad     Open Access   (Followers: 1, SJR: 0.161, CiteScore: 1)
Ingeniería, Investigación y Tecnología     Open Access   (Followers: 1)
Innovar     Open Access   (SJR: 0.118, CiteScore: 0)
Interações (Campo Grande)     Open Access  
Interface - Comunicação, Saúde, Educação     Open Access   (Followers: 1, SJR: 0.417, CiteScore: 0)
Intersticios Sociales     Open Access  
Intervención     Open Access  
Intervención Psicosocial     Open Access   (SJR: 0.381, CiteScore: 1)
Intl. Brazilian J. of Urology     Open Access   (Followers: 4, SJR: 0.367, CiteScore: 1)
Intl. J. of Morphology     Open Access  
Intl. J. of Odontostomatology     Open Access   (Followers: 1)
Intl. Law: Revista Colombiana de Derecho Internacional     Open Access   (Followers: 3)
Investigación Administrativa     Open Access  
Investigación Bibliotecológica     Open Access   (Followers: 6, SJR: 0.274, CiteScore: 0)
Investigación Económica     Open Access   (Followers: 4, SJR: 0.132, CiteScore: 0)
Investigación y Desarrollo     Open Access   (Followers: 1)
Investigación y Educación en Enfermería     Open Access   (Followers: 1, SJR: 0.198, CiteScore: 0)
Investigaciones Geográficas     Open Access   (SJR: 0.246, CiteScore: 0)
Investigaciones Marinas     Open Access  
Iteckne     Open Access  
Iuris Tantum Revista Boliviana de Derecho     Open Access  
Ius et Praxis     Open Access   (SJR: 0.283, CiteScore: 0)
Izquierdas     Open Access   (SJR: 0.188, CiteScore: 0)
Iztapalapa : Revista de ciencias sociales y humanidades     Open Access  
J. of Applied Oral Science     Open Access   (SJR: 0.645, CiteScore: 2)
J. of Applied Research and Technology     Open Access   (SJR: 0.255, CiteScore: 1)
J. of Coloproctology     Open Access   (SJR: 0.167, CiteScore: 0)
J. of Energy in Southern Africa     Open Access   (Followers: 3, SJR: 0.249, CiteScore: 1)
J. of Epilepsy and Clinical Neurophysiology     Open Access   (Followers: 7)
J. of Microwaves, Optoelectronics and Electromagnetic Applications     Open Access   (Followers: 11, SJR: 0.146, CiteScore: 1)
J. of Seed Science     Open Access   (Followers: 1)
J. of Soil Science and Plant Nutrition     Open Access   (Followers: 11, SJR: 0.823, CiteScore: 2)
J. of Technology Management & Innovation     Open Access   (Followers: 5, SJR: 0.271, CiteScore: 1)
J. of the Brazilian Chemical Society     Open Access   (Followers: 2, SJR: 0.357, CiteScore: 1)
J. of the Brazilian Society of Mechanical Sciences     Open Access   (Followers: 2)
J. of the Chilean Chemical Society     Open Access   (Followers: 2, SJR: 0.201, CiteScore: 1)
J. of the Mexican Chemical Society     Open Access   (Followers: 2, SJR: 0.214, CiteScore: 1)
J. of the Selva Andina Research Society     Open Access   (Followers: 3)
J. of the South African Institution of Civil Engineering     Open Access   (Followers: 2, SJR: 0.174, CiteScore: 0)
J. of the Southern African Institute of Mining and Metallurgy     Open Access   (Followers: 6)
J. of Venomous Animals and Toxins     Open Access   (Followers: 2)
JISTEM : J. of Information Systems and Technology Management     Open Access   (Followers: 7)
Jornal Brasileiro de Nefrologia     Open Access   (SJR: 0.334, CiteScore: 1)
Jornal Brasileiro de Patologia e Medicina Laboratorial     Open Access   (SJR: 0.143, CiteScore: 0)
Jornal Brasileiro de Pneumologia     Open Access   (SJR: 0.448, CiteScore: 1)
Jornal Brasileiro de Psiquiatria     Open Access   (Followers: 2, SJR: 0.224, CiteScore: 0)
Jornal da Sociedade Brasileira de Fonoaudiologia     Open Access  
Jornal de Pneumologia     Open Access  
Jornal Vascular Brasileiro     Open Access   (SJR: 0.136, CiteScore: 0)
Justicia Juris     Open Access  
Kriterion: Revista de Filosofia     Open Access   (Followers: 1, SJR: 0.114, CiteScore: 0)
Kronos : Southern African Histories     Open Access   (Followers: 6)
La ventana. Revista de estudios de género     Open Access  
La zaranda de ideas     Open Access   (Followers: 1)
Laboreal     Open Access  
Lankesteriana     Open Access   (SJR: 0.458, CiteScore: 1)
Latin American Applied Research     Open Access   (Followers: 1)
Latin American J. of Aquatic Research     Open Access   (SJR: 0.289, CiteScore: 1)
Latin American J. of Economics     Open Access   (Followers: 1, SJR: 0.127, CiteScore: 0)
Latin American J. of Solids and Structures     Open Access   (Followers: 4, SJR: 0.522, CiteScore: 1)
Latinoamérica. Revista de estudios Latinoamericanos     Open Access   (Followers: 2)
Lecturas de Economía     Open Access  
Letras Históricas     Open Access  
Límite : Revista Interdisciplinaria de Filosofía y Psicología     Open Access  
Linguagem em (Dis)curso     Open Access  
Lingüística     Open Access   (SJR: 0.13, CiteScore: 0)
Lingüística y Literatura     Open Access   (Followers: 1)
Literatura y Lingüística     Open Access   (Followers: 1, SJR: 0.13, CiteScore: 0)
Lua Nova : Revista de Cultura e Política     Open Access   (SJR: 0.274, CiteScore: 0)
Luna Azul     Open Access  
Machado de Assis em Linha     Open Access   (SJR: 0.101, CiteScore: 0)
Madera y Bosques     Open Access  
Maderas. Ciencia y tecnología     Open Access   (Followers: 2, SJR: 0.546, CiteScore: 1)
Magallania     Open Access   (SJR: 0.354, CiteScore: 0)
Mana - Estudos de Antropologia Social     Open Access   (Followers: 2, SJR: 0.355, CiteScore: 0)
Manuscrito     Open Access  

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Journal of the Brazilian Chemical Society
Journal Prestige (SJR): 0.357
Citation Impact (citeScore): 1
Number of Followers: 2  

  This is an Open Access Journal Open Access journal
ISSN (Print) 0103-5053 - ISSN (Online) 1678-4790
Published by SciELO Homepage  [887 journals]
  • What is new for 2020

    •  
  • Serpentinites: Mineral Structure, Properties and Technological
           Applications

    • Abstract: Serpentine is a versatile mineral family rich in Mg silicate with several polymorphic phases, mainly antigorite and lizardite, all of them with similar chemical composition (Mg3Si2O5(OH)4). Their structures are generally composed of octahedral layers rich in Mg[MgO2(OH)4]6- , attached to a tetrahedral silicate [Si2O5]2- sheet. The unique physicochemical properties of serpentinites and the existence of large reserves in Brazil create new important opportunities for research and technological applications. In this work, serpentinites structures and properties are reviewed, as well as its occurrence and literature describing its applications in construction/ceramics, agriculture, as a silica source, in steel production, as an additive/filler in polymers, in the production of composites, adsorption of cations and organics contaminants, CO2 capture and catalysis. The presence of harmful chrysotile associated with serpentinites, some of its properties and uses are also described.
       
  • Use of Arduino in the Development of a New and Fast Automated Online
           Preconcentration System Based on Double-Knotted Reactor for the Mn
           Determination in Tea Samples by Flame Atomic Absorption Spectrometry (F
           AAS)

    • Abstract: In the present paper, an automated online preconcentration system based on the use of two knotted reactors (KR) was developed for Mn determination in tea samples by flame atomic absorption spectrometry (F AAS). The system automation was performed by using four solenoid valves to switch sample streams and reagents. Valves were driven electronically by an integrated Darlington transistor circuit and controlled by an open-source Arduino hardware platform written in C language. The preconcentration was based on the precipitation process of metal ions complexed with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol (5-Br-PADAP) on the inner walls of the reactor, followed by elution with a solution of hydrochloric acid. The optimized system allowed the Mn determination with limit of detection (LOD) of 2.1 mg L-1, precision (relative standard deviation (RSD), 50.0 mg L-1) of 2.6% and enrichment factors of 8. The system presented a sampling frequency of 60 h-1. The method accuracy was evaluated by analysis of the certified reference material (CRM) apple leaves (NIST 1515) and by addition/recovery tests obtaining recoveries between 95.2 to 119%. This method was applied in the Mn determination in commercial tea samples purchased from local trade. Manganese levels were found in a concentration range of 2.95 to 123 µg g-1.
       
  • Determination of Catechol and Hydroquinone by Using Perilla frutescens
           Activated Carbon Modified Glassy Carbon Electrode

    • Abstract: High specific surface area activated carbon prepared by Perilla frutescens (PFHSAAC) was modified on the surface of the glassy carbon electrode (GCE) by drop-coating method to construct a PFHSAAC/GCE. The electrochemical properties of the modified electrode were investigated in detail by some electrochemical methods such as cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Experiment results show that the modified electrode has excellent redox activity and distinction capability toward the two isomers of catechol (CC) and hydroquinone (HQ). The separation of oxidation peak potential for HQ and CC of DPV is 112.8 mV. Under the optimal conditions, the oxidation peak currents of HQ and CC show good linear relationships with their concentrations in the ranges of 1.0 × 10-6-2.0 × 10-4 and 1.0 × 10-6-1.5 × 10-4 mol L-1, respectively. The limits of detection for HQ and CC are 3.57 × 10-7 and 4.23 × 10-7 mol L-1, respectively. The PFHSAAC/GCE exhibits good stability, repeatability and sensitivity. The developed method was used to determine HQ and CC in water samples with best results.
       
  • Direct Analysis of Human Hair Before and After Cosmetic Modification Using
           a Recent Data Fusion Method

    • Abstract: The cosmetic modification of hair is a very common procedure used to mask or cover evidence at a crime scene. Deoxyribonucleic acid (DNA) tests are expensive and require good-quality collection of samples and a database profile. To overcome these challenges, direct analysis was performed on a large set of hair strands collected from individuals, denoted original samples, and the data were compared with those of the same samples after cosmetic modification performed by bleaching the samples in the laboratory. A total of 127 samples were evaluated in this study using two analytical techniques, wavelength-dispersive X-ray fluorescence (WDXRF) and laser-induced breakdown spectroscopy (LIBS). Instead of testing many algorithms to develop classification models for the original and bleached samples, a recent method was applied that combines information from 17 classifiers. Data fusion was also evaluated to improve the accuracy of the classification model, which was higher than 99.2%, with no requirements to select eigenvectors or thresholds.
       
  • New Proposal for Sugarcane Vinasse Treatment by Hydrothermal
           Carbonization: An Evaluation of Solid and Liquid Products

    • Abstract: Vinasse is a residue of ethanol production from sugarcane. In view of the problems associated with its disposal, this study aimed to propose a treatment for vinasse by hydrothermal carbonization. The influence of temperature (100 to 200 ºC), acidity (1.7 to 8.3%) and reaction time (12 to 48 h) on the hydrothermal treatment was evaluated, as well the characteristics of the solid (hydrochar) and liquid (process water) products. For the solid product, two hydrothermal carbonization conditions stood out as leading to higher carbonization and yields. These conditions were 200 ºC, 8.3% acidity and times of 12 and 48 h. For the process water, the carbonization reaction at 200 ºC, 8.3% acidity and 48 h produced the highest discoloration and 77% reduction of total organic carbon. Thus, hydrothermal carbonization proved to be an efficient method to treat vinasse, and the hydrochar presents potential for use as fertilizers / soil conditioners, and also the process water after pre-treatment.
       
  • Investigating Surface Properties and Lithium Diffusion in
           Brookite-TiO2

    • Abstract: Surfaces properties of TiO2 in the brookite phase and the lithium diffusion are studied using density functional theory (DFT) and interatomic potential simulations. Simulations predict that the brookite surfaces have a higher intrinsic Lewis acidity compared to the other polymorphs due to the presence of four coordinated Ti atoms on the surface in contrast to the most stable surfaces of anatase and rutile which have five coordinated Ti surface atoms. The surface reactivity of the brookite is then expected to be higher for catalysis. The (210) surface is the most stable calculated surface and some experimental morphologies have been revisited. Regarding Li intercalation, the migration occurs along the c-direction and open channel surfaces are desired, therefore particles exposing the (001) surface. Those differences on chemical/physical properties highlight the importance to control the nanoparticle shapes for a given application.
       
  • Synthesis, Characterization and Conformational Analysis of Two Novel
           4(1H)‑Quinolinones

    • Abstract: Quinolinones are a class of organic compounds known as alkaloids found in several plants and also can be synthesized. Their large use in therapies regards their wide biological potential like antitumor, psychiatric and neurological agents. Two substances were structurally characterized: (E)-3-(2-nitrobenzylidene)-2-(4-methoxyphenyl)-1-(phenylsulfonyl)-2,3-dihydroquinolin-4(1H)‑one (NMQ), and (E)-3-(2-chlorobenzylidene)-2-(2-methoxyphenyl)-1-(phenylsulfonyl)-2,3‑dihydroquinolin-4(1H)-one (CMQ). These compounds were synthesized, crystallized, characterized by single crystal X-ray diffraction and theoretical calculations. The NMQ and CMQ crystals are formed by a pair of enantiomers and crystallized in the centrosymmetric group P21/c with similar volume and density. Differences noted on crystal packing and supramolecular arrangement are associated to substituent group chlorine in CMQ and nitro in NMQ. The calculated infrared (IR) spectra show a good agreement with experimental values. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies show CMQ more kinetically stable with a higher resistance to transfer charge than NMQ.
       
  • Integrative Approach Based on Leaf Spray Mass Spectrometry,
           HPLC-DAD-MS/MS, and NMR for Comprehensive Characterization of
           Isoquinoline-Derived Alkaloids in Leaves of Onychopetalum amazonicum R. E.
           Fr.

    • Abstract: Onychopetalum is an Amazonian botanical genus close-related with Bocageopsis and Unonopsis, whose species are used in traditional medicine. Although these genera are widely investigated from the phytochemical viewpoint, the knowledge about Onychopetalum remains almost unexplored. In order to perform a comprehensive characterization of isoquinoline-derived alkaloids from Onychopetalum amazonicum, an integrative approach based on the alkaloid profile analysis by leaf spray mass spectrometry (LS-MS), followed by a robust dereplication through high-performance liquid chromatography coupled with diode array detector and atmospheric pressure chemical ionization tandem mass spectrometry, (HPLC-DAD-APCI-MS/MS) and nuclear magnetic resonance (NMR) analysis was adopted. LS-MS allowed the tentative identification of reticuline, norjuziphine, nornuciferine, O-methylisopiline, nuciferine, N-methyl-O-methylisopiline, anonaine, and N-methylanonaine. HPLC-DAD-MS/MS analysis supported the tentative identification of N-methylasimilobine, asimilobine, norushinsunine, N-methylisopiline, isopiline, liriodenine, and lysicamine. Moreover, the integration of MS and NMR data allowed the additional identification of stepholidine and isocorypalmine. The applied integrative approach proposed herein enabled a comprehensive analysis of the alkaloid content from the O. amazonicum, showing to be a useful strategy for the dereplication of isoquinoline-derived alkaloids.
       
  • Acid-Catalyzed Z-E Isomerization of γ-Alkylidenebutenolides: An
           Experimental and DFT Study

    • Abstract: The Z-E isomerization of γ-alkylidenebutenolide analogues to natural nostoclides and other natural butenolides was investigated using 1H nuclear magnetic resonance (NMR) and high performance liquid chromatography (HPLC) data as well as density functional theory (DFT) calculations at the wB97x-D/6-31G(d,p) level, including solvent effects with the polarizable continuum solvation approach. The experimental data supported the Z to E isomerization of γ-alkylidenebutenolides under acid catalysis. Newly prepared samples have predominantly Z configuration, which partially isomerizes to the E isomer under acidic conditions. Density functional theory studies corroborate the experimental findings. While neutral γ-alkylidenebutenolides are more stable in the Z form, protonation of the γ-lactone carbonyl group results in preferential stabilization of the E isomer.
       
  • Performance of Avocado Seed Activated Carbon as Adsorbent for Highly
           Sensitive Determination of Cd Using a Flow Injection System Online Coupled
           to TS-FF-AAS

    • Abstract: A flow-injection preconcentration system using detection by the thermospray flame furnace atomic absorption spectrometry (FIA-TS-FF-AAS) is proposed. Cd2+ are adsorbed on avocado seed activated carbon (ASAC) packed into a cylindrical mini-column and eluted using HCl solutions for the detection system. A 25–1 fractional factorial and Doehlert matrix design were employed to determine the optimum conditions for cadmium preconcentration (pH 7.68, buffer concentration (Tris/Tris-HCl) of 0.023 mol L-1, eluent concentration (HCl) of 2.0 mol L-1, the adsorbent mass of 100.0 mg and preconcentration flow rate of 4.8 mL min-1). The preconcentration method presents linearity within the range of 0.41-15.00 µg L-1, limits of quantification and detection of 0.41 and 0.12 µg L-1, respectively, preconcentration factor of 10.7, consumption of index of 0.93 mL and sample throughput of 26 h-1. The precision assessed as the relative standard deviation (RSD) were found to be 0.48, 0.90 and 2.30% for inter-day precision (n = 2), and 0.30, 0.44 and 2.48% for intra-day precision (n = 6) for respective cadmium concentration of 0.50, 5.00 and 15.00 µg L-1. The proposed method was applied satisfactorily in samples of cigarette (62.84 ± 11.28 µg kg-1), human hair (69.61 ± 2.38 µg kg-1) and water samples [lake (0.65 ± 0.01 µg L-1), tap and mineral].
       
  • Magnetic Solid-Phase Microextraction for Lead Detection in Aqueous Samples
           Using Magnetite Nanoparticles

    • Abstract: A magnetic solid-phase microextraction procedure was developed to detect lead in aqueous samples by flame atomic absorption spectrometry (FAAS). Fe3O4 nanoparticles were synthesized by coprecipitation and the crystalline phase was confirmed by X-ray diffraction. The point of zero charge (PZC) indicated that the oxide surface was negatively charged at pH levels above 9.4. pH 9.0 is the best for adsorption and the influence of stirring time and adsorbent mass were analyzed and set at 4 min and 3.0 mg, respectively. The best desorption conditions were obtained for 500 µL of 0.5 mol L-1 HNO3 as eluant. The limit of quantification (LOQ) and relative standard deviation (RSD) were 16.48 µg L-1 and 0.25%, respectively. The linear range was found to be 16.48‑500 µg L-1. The accuracy was evaluated by recovery tests in mineral water, micellar water and aqueous makeup remover samples, showing values in the range of 95.94 to 118%.
       
  • Strontium Oxide Decorated Iron Oxide Activated Carbon Nanocomposite: A New
           Adsorbent for Removal of Nitrate from Well Water

    • Abstract: In the present study, activated carbon was magnetized by iron oxide and modified by strontium based nanoparticles (FeAC@Sr) to introduce it as an efficient favorable adsorbent for the removal of nitrate ions from underground water. The decorated adsorbent was characterized in terms of size, structure, morphology and composition using scanning electron microscopy, Fourier-transform infrared spectroscopy and energy dispersive X-ray spectroscopy. The equilibrium adsorption data were well fitted and explained by Langmuir isotherm with a maximum adsorption capacity of 87.42 mg g-1 (theoretical value calculated from the Langmuir isotherm model). Regarding adsorption kinetic it was seen that it is fit for pseudo-second-order process with an equilibrium state which was reached at pH 4.0 in 90 min. The results also revealed that the incorporation of positively charged strontium and iron oxide into the activated carbon has triggered removal efficiency for the negatively charged nitrate ions.
       
  • Concomitant Production of Hydrogen, Sodium Acetate, and Polymerized
           Species from Non-Catalytic Ethanol Dehydrogenation

    • Abstract: A detailed study of the production of hydrogen and high added-value liquid products from the ethanol dehydrogenation reaction in the presence of sodium hydroxide (10% m m-1) was undertaken. Experiments were carried out in a batch reactor under different reaction conditions (temperature of 240 ºC and autogenous pressure between 45 and 72 bar), with analysis of the products obtained in the gas, liquid and solid fractions. The results showed that hydrogen was the major product formed in the gaseous fraction (maximum of 86.9%), while sodium acetate was the product in the solid fraction. Studies of the reaction mechanisms confirmed formation of the products identified in the gaseous and solid fractions. Mass spectrometry analyses of the liquid fractions revealed the presence of a series of compounds with molecular masses considerably higher than that of ethanol, which could be explained by the favoring of anionic polymerization reactions, under the experimental conditions employed.
       
  • Multi-Element Evaluation in Black Pepper (Piper nigrum L.)
           According to the Processing

    • Abstract: Black pepper is one of the most consumed spices worldwide and the evaluation of trace elements content is essential to promote consumer safety. In this study, concentrations of the elements As, Cd, Co, Cu, Fe, Mn, Mo, Ni, Pb, Se, V and Zn was determined in samples of black peppercorn (n = 25) and ground black pepper (n = 25) to verify how processing affects element concentrations. The elements were determined by inductively coupled plasma mass spectrometry and flame atomic absorption spectrometry. A principal component analysis showed that Fe, Pb and V was influenced by the processing and ground black pepper samples showed higher levels for these elements than black peppercorn. Although specific legislation for spices is not available in Brazil, results indicated that Pb concentrations in two brands of the processed samples under investigation exceeded the maximum level established by Brazilian and European legislation for vegetables and fruits. These results point to the necessity to control the processing of the black pepper, especially the grinding step.
       
  • Dextrorotatory Chromomycins from the Marine Streptomyces sp. Associated to
           Palythoa caribaeorum

    • Abstract: A Streptomyces sp. (BRA-384) was selected among nine strains of bacteria isolated from the zoanthids Palythoa caribaeorum due to the high cytotoxic activity presented by its EtOAc extract (inhibitory concentration mean (IC50) of 2 ng mL-1) against colon cancer cell line. From the EtOAc extract of BRA-384 three new chemical entities (A6, A7 and A8) and one dextrorotatory chromomycin (A5), a promising class of anticancer compounds, were identified. The cytotoxicity of chromomycins A5 to A8 was tested against five tumor cell lines (HCT 116 (human colon adenocarcinoma), MCF-7 (human breast carcinoma), PC-3M (human metastatic prostate cancer), 501-mel (human metastatic melanoma) and MM200 (metastatic melanoma)). All chromomycins were highly potent showing IC50 values from 0.2 to 133 nM. Chromomycin A5 was consistently the most potent over all tested cells (IC50 values from 0.2 in MM200 to 7.9 nM in PC-3M), inclusive when compared to the standard chemotherapeutic agent doxorubicin, that presented IC50 values ranging from 147 to 568 nM against MM200 and MCF-7, respectively.
       
  • Solvothermal Synthesis of Cerium-Doped Titania Nanostructured Materials
           Modified with Acetylacetone for Solar-Driven Photocatalysis

    • Abstract: This study reports the preparation of nanostructured cerium-doped titanium dioxide photocatalysts containing different cerium concentrations by a modified sol-gel route involving the use of acetylacetone. The nanocrystalline powders had their structural, morphological, and optical properties characterized by X-ray diffraction, vibrational and Raman spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, Brunauer, Emmett and Teller (BET) surface area analysis, scanning electron microscopy combined with energy dispersive X-ray spectroscopy, total reflection X-ray fluorescence, and diffuse reflectance spectroscopy. Cerium incorporation reduced the bandgap energy of the solids to values that allowed them to absorb visible light. Cerium presence improved the textural properties that are crucial for the catalytic process. The photocatalytic activities were evaluated through photodegradation experiments of methyl orange dye solution. The synthesis with acetylacetone as stabilizer provided nanostructured materials with higher Ce3+/Ce4+ ratio, which enhanced the photocatalytic activity. Smaller quantities of the doped photocatalysts afforded higher degradation rates than the rates reported in the literature.
       
  • Selective Inner-Filter on the Fluorescence Response of Chlorophyll and
           Pheophytin Molecules Extracted from Caesalpinia echinata Leaves

    • Abstract: Photophysical processes in multicomponent solutions composed by natural pigments, extracted from Caesalpinia echinata (Brazil-wood) leaves, are investigated. Beacuse of the main fluorescent molecules in these solutions are the chlorophyll a, chlorophyll b and pheophytin a, all features are discussed regarding these three pigments. It is observed that the fluorescence bands of these macrocyclic molecules, located around ca. 673 nm, are progressively quenched due to the increase of the solutions’ concentration. Due to a significant overlapping between their fluorescence and absorption Q-bands, it is concluded that the inner-filter effect causes such quenching. Through analysis of steady-state and time-resolved fluorescence, it is verified that the inner filter acts more effectively on the emission assigned to chlorophyll a. Invoking reported extinction coefficients for these pigments in their isolated forms, we can give a qualitative interpretation of such selectivity considering the effectiveness of the overlapping between the absorption and fluorescence bands.
       
  • Well Defined Rich Electronic Structure: Facile Approach for Nido-Carborane
           Fused Azaspirodecaniums in Water Solution

    • Abstract: A novel bis-dumbbell shape of a multi cation around a azaspirodecanium combined with nido-carborane was prepared in a single step in good yield starting from pyrrolidine and 1,3-dichloropropane to give one compound and from piperidine and 1,4-dichlorobutane to give the other. This is the first report of an electrolyte azaspirodecanium-boron-cluster structure. 1H,13C, and 11B nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and high resolution mass spectrometry (HRMS) methods revealed changes due to interactions among the functional groups. In particular, the compound was electron-rich because of its unique structure and excellent chemical reactivity.
       
  • Microwave Assisted Ultra-Fast Method to Synthesize Carbonate-Phosphates,
           Na3MCO3PO4 (M = Mn, Fe, Co, Ni) - Relevant Materials Applied in Sodium-Ion
           Batteries

    • Abstract: Although largely used in mobiles and electric vehicles applications, insertion batteries based on Li-ion technology are high-cost devices. These applications require high-performance energy storage systems with high-energy and high-power densities, which are better attained by Li-ion technology. However, stationary applications such as power plants and uninterruptible power supplies (UPS) mainly require low-cost energy storage devices. In this scenario Na-ion insertion batteries feature as a cheaper option for such applications. Among the several compounds for use as cathode in Na-batteries, a largely studied class of compounds are the sodium-carbonate-phosphates, Na3MCO3PO4 (M = Mn, Fe, Co or Ni), with structure analogue to the mineral sidorenkite. In this work, it was developed a new microwave-assisted hydrothermal method as an ultra-fast way to prepare sodium-carbonate-phosphate compounds. This methodology results in high-quality materials with general formula Na3MCO3PO4 (M = Mn, Fe, Co or Ni) upon only 5 min processing time. Characterization techniques indicate highly ordered materials with sidorenkite-like phase and different morphologies or crystal habits, including plates, rods, and a ‘starfruit’ shape. As a proof-of-application the Mn-based material was evaluated from electrochemical tests for Na+ insertion reactions. The obtained results evidence initial discharge capacity of 107 mA h g-1 with good reversible capacity (65 mA h g-1) after several charge/discharge cycles.
       
  • Resorcinolic Lipids from Yucatecan Propolis

    • Abstract: Propolis is a material produced by bees from a combination of plant exudates and wax, used to fill out cracks in the beehive and to defend against intruders and pathogenic microorganisms; it is recognized for its many biological activities and its chemical composition depends on the botanical sources close to the beehive. The objective of this investigation was to isolate and identify metabolites with antioxidant activity present in a propolis sample collected in Yucatan, Mexico. Purification of the bioactive metabolites was carried out using argentation chromatography, while the combination of 1H nuclear magnetic resonance (NMR), laser desorption ionization (LDI), gas chromatography-mass spectrometry (GC-MS) and biosynthetic origin data allowed their identification as resorcinolic lipids. Finally, the resin of Mangifera indica was identified as the botanical source of these metabolites.
       
  • Cytotoxic Activity of Synthetic Chiral Amino Acid Derivatives

    • Abstract: Cancer is a chronic degenerative disease considered one of the most important causes of death worldwide. In this context, a series of dual-protected amino acid derivatives was synthesized and evaluated as potential novel anticancer agents. The 40 derivatives were prepared in up to three reaction steps. The cytotoxic activities were screened in vitro against a panel of tumor and non-tumor cells using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Among the synthesized derivatives, three of them showed promising activity against cancer cells with half-maximal inhibitory concentration (IC50) ranging between 1.7-6.1 µM. The most promising derivative, bearing both a lipophilic N-alkyl diamine moiety and a protected amino acid scaffold showed a selectivity index of 3.4 towards tumor cells. The N-alkyl diamine moiety seems to play a crucial role in the enhancement of the anticancer activity. On the other hand, the incorporation of an amino acid scaffold resulted in increase in the selectivity towards cancer cell lines.
       
  • TiO2 Decorated Sand Grains for Photodegradation of Pollutants: Methylene
           Blue and Ciprofloxacin Study

    • Abstract: This study shows a preparation and evaluation of a new non-expensive TiO2 based photocatalyst built over sand grains surfaces as an alternative green technology for water treatment. The semiconductor covalently bonded to the silica sand grains (sand@TiO2) prepared by hydrolysis of isopropoxide orthotitane over sand grains, showed a high surface area 296 m2 g-1 and a high reaction rate for methylene blue (MB) photodegradation (0.064 min-1), on steady state condition by using 3 g of sand@TiO2 and an MB solution (20 mL, 3 × 10-5 mol L-1) or ciprofloxacin hydrochloride (CIP) solution (20 mL, 1.9 × 10-3 mol L-1). Under UV irradiation with a medium pressure Hg lamp, the total MB removal reached 70% after 7 min and 45% for CIP in 60 min. Further, the photocatalyst showed to be a promising reusable material for removal of ciprofloxacin hydrochloride antibiotic (CIP) on wastewater. This new material appears as a new promising low cost and low impact reusable catalyst for water treatment.
       
 
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